There is known a technique of managing energy in a machine, which has a supply part for supplying energy and a consume part for consuming the energy supplied by the supply part. Such a technique is disclosed in, for example, Japanese Laid-Open Patent Application No. 8-507671. One example of the supply part is a battery cell as an electric-energy accumulating part, and another example is a generator as an electric-energy generating part. On the other hand, one example of the consume part is an electric motor that is driven to provide a drive force to a machine.
In a machine that performs a work, energy is consumed to as to perform the work. The energy to perform a work may be supplied to the machine from outside, or the machine itself has an energy source to supply a necessary energy by itself. In any case, energy consumed by a machine is limited, and, thus, there is a great demand for saving energy while achieving a target operating condition. Therefore, there is a strong demand for the same machine to achieve both a target operation condition and energy saving.
There may be a case in which the above-mentioned machine has a plurality of actuators that may be driven simultaneously. In such as case, it is not easy to achieve both the target operating condition and the saving of energy consumption. It is theoretically possible to set the capacity of an energy source beforehand so that an energy source does not deplete even if all the actuators are driven simultaneously. However, judging from economical viewpoints or physical viewpoints such as weight, size, etc., it cannot be said that the above-mentioned means is a realistic solution.
There is a technique to comprehensively manage a plurality of actuators provided in an automobile as a machine using fuel as an energy source. In the case of an automobile, the plurality of actuators are an engine, a braking apparatus, a driving apparatus, a steering apparatus, etc. Such a technique is disclosed in, for example, Japanese Laid-Open Patent Application No. 5-85228.
The inventors have researched and investigated an energy management technique for a machine having a supply part for supplying energy and a consume part for consuming the energy supplied by the supply part, and acquired the following knowledge and information.
That is, since the consume part is provided in the machine for the purpose of achieving a certain target, and also driven by energy supplied by the supply part, it is desirous to achieve both the requirements from machine operation and the energy saving by the consume part. Additionally, in order to determine whether or not the consume part is driven so that the consumed energy is actually saved, it is important to monitor the actual energy efficiency of the consume part.